1. Field of Invention
The present invention relates to a recombinant fusion antigen gene, a recombinant fusion antigen protein and a subunit vaccine composition having the same for animal use. More particularly, the present invention relates to a recombinant fusion antigen gene, a recombinant fusion antigen protein and a subunit vaccine composition having the same against infection of porcine reproductive and respiratory syndrome virus.
2. Description of Related Art
Porcine reproductive and respiratory syndrome (PRRS) was first reported in the Northern America in 1987. Several years later, PRRS and results in global outbreaks successively and great economic losses of the swine industry. As for the global swine industry, the urgent problem to be solved is how to prevent and control PRRS. PRRS probably occurs in all ages of pigs, resulting in physiological disorders, respiratory tract syndrome and death. PRRS is caused by porcine reproductive and respiratory syndrome virus (PRRSV). PRRSV belongs to the Arteriviridae family, including a positive-sense, single stranded RNA genome with viral envelope, and the diameter of the virus particle is 50-70 nm. The PRRSV genome is approximately 15 kb in the full length and encodes 10 open reading frames (ORFs). 26 kDa of glycoprotein 5 (GP5) is encoded by ORF5 and 19 kDa of unglycosylated membrane protein (M) is encoded by ORF6.
There are three major types of commercial PRRS vaccines, including live attenuated vaccines, killed vaccines and subunit vaccines produced by Escherichia coli (E. coli). The live attenuated vaccines can stimulate cellular and humeral immune responses, but the titer of the neutralizing antibody is less, resulting in insufficient protection ability and the risks of virulent spread and virulent recovery. The killed vaccines have no the risks of virulent spread and virulent recovery; however, the killed vaccines merely evoke the humeral immune response and they cannot provide protection ability against heterologous virus infection, so that it is necessary to immunizing the killed vaccines twice for providing a sufficient protection ability. In addition, there is no exact data to show that the subunit vaccines produced by E. coli can provide sufficient protection ability.
The PRRSV evolves and mutates extremely fast due to RNA virus. There is, however, a growing need for new vaccines with safety and protection ability without no risks of virulent spread and virulent recovery is emerging, for overcoming all issues of conventional vaccines.